A number of technologies attempt to identify the location of mobile devices by estimating the distance between the devices and known beacon locations. In some such methods, a mobile device measures the received strength of wireless signals sent by multiple beacons, applies a wireless propagation model to the received signal strength values to estimate the distances between the mobile device and the beacons, and applies a trilateration technique (e.g., the method of circles) to the estimated distances to identify a likely location of the mobile device.
However, simple propagation models do not account for common environmental factors that can significantly affect the strength of received signals, such as walls and other barriers, mobile device casings, and orientation and obstruction of the antenna. More complex models require computational power beyond that available in a mobile device, or a high degree of prior knowledge of the physical surroundings of the mobile device.